In a conventional well-known electronic packaging technology, to mount an electronic component onto a substrate, a bonding tool having a suction opening holds an electronic component against a release tape by a suction force, presses the electronic component against an adhesive agent that is applied on the substrate, and heats the electronic component. More particularly, the bonding tool holds a release tape, which is a releasable fluorinated tape, by a suction force and then forms an opening on the fluorinated tape with a needle in such a manner that the opening is aligned with a chip suction opening of the bonding tool. The bonding tool then holds a chip by a suction force and then mounts the chip onto the substrate.
With the modern trend of slimming large-scale-integration (LSI) packages, slim electronic components (chips) and flip chips are used more and more as embedded components. In multi-chip implementations where layered electronic components are formed inside a package, in some cases, an overhang is formed, i.e., an upper chip (second electronic component) overhangs the circumference a lower chip (first electronic component).
If an overhang occurs, as the thickness of the chip decreases, issues of concern occur, such as a decrease in the performance of upper-chip wire bonding and chip breakage. To prevent the problems caused by an overhang, such as a decrease in the performance of upper-chip wire bonding and chip breakage, an approach is considered to reinforce the overhang with an adhesive agent (underfill material) that is applied to a substrate before a lower chip is mounted on the substrate by protruding the adhesive agent out from the circumference of the lower chip. According to this approach, the upper chip is mounted on an area including both the upper surface of the lower chip and a protruding part of the upper surface of the underfill material.
However, if a lower chip is mounted onto a substrate using the above conventional overhang reinforcing technology, because the release tape is expanded by heat and a folded line is formed, the folded line is transferred onto the underfill material protruding out from the circumference of the lower chip.
The fluorinated tape is not held in place: due to heat (for example, approximately 200° C. or higher) coming from the bonding tool during chip mounting, the fluorinated tape that is made of, for example, a polytetrafluoroethylene (PTEE) film is expanded and a folded line is formed between an expanded part and a non-expanded part. The folded line extends to an area where the underfill material is formed as a fillet and, therefore, the folded line is formed on the fillet.
If a folded line is transferred onto the upper surface of the underfill material on which the upper chip is mounted, there is a possibility of a decrease in the performance of the upper-chip wire bonding, a crack forming during wire-bonding, a decrease in the adhesivity of the adhesive surface on which the chip is mounted, etc. Moreover, if an excess amount of the adhesive agent is supplied accidentally because of poor control over the amount of adhesive agent supplied, an issue of concern arises in that the excess adhesive agent may contaminate adjacent components. The above problems occur regardless of the type of the underfill material (sheet or paste) and the type of the adhesive agent of the upper chip (sheet or paste). If the thickness of the upper chip is approximately 200 μm or lower, the possibility of breakage becomes high.
Even if no more chips are mounted, i.e., only one chip is mounted, when an excess amount of adhesive agent is supplied because a folded line is formed, an issue of concern arises in that the excess adhesive agent contaminates a wiring pattern.
Patent document 1: Japanese Laid-open Patent Publication No. 2003-7771
Patent document 2: Japanese Laid-open Patent Publication No. 2006-66767